Pull-ups are a common exercise performed by people for training arm, shoulder, and back muscles. They involve gripping a constrained object with the individual's arms, suspending all or part of the individual's body weight on the arms, and lifting the individual's body upwards utilizing muscular effort. Despite requiring a certain minimum level of fitness in order to execute pull-ups, they offer many advantages in comparison to other popular types of arm exercises such as push-ups, arm curls, and bench presses. Compared with push-ups, pull-ups exercise more stabilizing muscle groups, they utilize the full body weight of the individual, and they place him or her in a vertical orientation, which may be found more natural and comfortable than the face down horizontal position required for push-ups. Compared with arm curls and bench presses, pull-ups utilize the individual's body weight as load, so the equipment required can be made significantly less heavy and more portable. In certain places, they require no extra equipment at all. Outdoors, pull-ups can be executed using elements of the natural environment, such as tree branches, or of the built environment, such as playground equipment. Indoors, however, few locations tend to have features which are suitable to being gripped by one's arms and having the individual's full or partial weight subjected upon them.
A significant number of devices have been invented in an attempt to rectify the relative lack of indoor features suitable for performing pull-ups in typical home or office environments. Many of these devices are intended to be secured to a door frame. Some, such as U.S. Pat. No. 7,066,866 B1 to Mobley, are full width horizontal pull-up bars meant to be affixed to a specific door permanently. The installation procedure involves securing the device to the target door with screws. Moving the device from one door to another may be a time consuming and relatively complex process, which the user may not wish to perform as frequently as doing pull-up exercise sessions. Having the device installed may also limit the height of the door opening, forcing taller individuals to duck under the permanent pull-up bar.
Devices which may be removed easily and quickly for individual sessions of pull-up exercises avoid the shortcomings of permanent doorway mounted pull-up bars. One popular design is described in U.S. Pat. No. D,348,706 to Harrell. It is a doorway mounted pull-up bar which may be installed onto a doorway quickly and also removed quickly. The device is substantially bulky, having a main grip bar extend horizontally beyond the edges of the door and a number of auxiliary bars attached to the main grip bar. As a result of this, the device cannot be installed onto doors wider than the fixed width of the main grip bar. Furthermore, because the main grip bar is uninterrupted across its width, in the course of a pull-up, the individual must pull back their head to avoid physical contact between the individual's face and the main grip bar. Despite these drawbacks, embodiments of this design enjoy tremendous consumer popularity. Several of such embodiments are regularly top sellers on websites such as amazon.com, and at the time of writing, one of these embodiments is the 20th highest selling fitness item on amazon.com.
The bulkiness of the previous device is largely addressed by U.S. Pat. No. 7,993,245 to Dorfman, a profiled strip intended to be installed on top of a door for performing pull-ups. It possesses significant size and weight advantages over the previously discussed designs, however, due to the elongated body intended to cover the length of a door, it suffers from limited portability compared to the opposably mounted design claimed herein. It also suffers from awkward exercise posture: because the device is installed directly on the upper edge of a solid door, the user may have to keep pushing their body away from the door while performing a pull-up. The same limitation is shared by the chin-up assembly described in U.S. Pat. No. 7,601,100 to Hinds and Bonneville.
U.S. Pat. No. 6,503,175 to Harrell describes a portable exercise device made up of two separated clamp members that are secured onto a support frame by a length-adjustable flexible attachment member which is interwoven between the clamp members. While the goals of this device are very similar to those of the present invention, the clamping mechanism is significantly less secure. Unlike the present invention which includes a pivotal joint, the clamping members described in U.S. Pat. No. 6,503,175 are pressed against the lip of the support frame directly by a flexible attachment member in combination with a body second edge. However, because the flexible attachment member is almost vertical at the attachment point, constrained by the geometry of the door frame, the inward horizontal component of the clamping force is a small fraction of the vertical component. Thus, only inward facing, ‘hook’ edges, or edges with a high coefficient of friction, are suitable for securing this device. The present invention incorporates a pivotal connection between the clamp members which uses the rotational torque from the supported individual's weight to push the clamping members off each other and horizontally into the support structure, allowing a secure, self-energizing connection to a wide range of support structure shapes.